The document covers error handling in C, detailing types of errors, differences between errors and exceptions, and the benefits of error handling. It explains how exceptions are generally runtime problems not directly supported by C, and outlines methods for exception handling, including the if-else method and setjmp()/longjmp() method. Additionally, the document emphasizes the importance of pre-defined procedures for managing exceptions and maintaining program stability.

1. Error Handling
Md. Imran Hossain Showrov (showrovsworld@gmail.com)
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2. Outline
 Errors and Its Types
 What is an Exception?
 Differences Between an Error and an Exception
 Benefits of Error Handling
 Exception Handling in C
 Methods of Exception Handling

3. Errors and Its Types
 There are three basic types of errors:
1. Syntax Error
2. Semantic Errors
3. Logical Errors

4. Errors and Its Types (cont..)
 These errors are detected by the ‘C’ compiler.There
are also a few kinds of errors in ‘C’ those are not
detected by the compiler.
1. Run Time Errors
2. Compile Time Errors
.These error are not identified by the compiler and so
they are termed as “EXCEPTIONS”

5. What is an Exception?
 An exception is an indication of a problem that
occurs during a program’s execution.
 Exception is a runtime problem that occurs rarely
handling an exception allows programs to continue
executing as if no problem had been encountered.
 Helps terminating the program in a controlled
manner rather in an unpredictable fashion
 Exception handling enables programmers to create
applications that can resolve (or handle) exceptions

6. Differences Between an Error and an
Exception
 Errors occur at compilation time as well as run time while
exceptions mostly occur at run time.
 Compile time errors are detected by the compiler while
exceptions need to be predicted by the programmer himself
 Errors occur frequently while exceptions, as the name
suggests occur seldom
 Error detection and debugging is easier while exception
prediction and its handling is a bit complex procedure
 Errors can be removed by removing syntax and logical
mistakes while exception handling needs pre-defined or user
defined procedures

7. Benefits of Error Handling
 Helps improve a program's fault tolerance.
 Enables the programmer to remove error-handling
code from the ‘main line’ of the program’s execution
 Programmers can decide to handle any exceptions
they choose – all exceptions of a certain type or all
exceptions of a group of related types

8. Exception Handling in C
 C does not provide direct support for
error/exception handling.
 By convention, the programmer is expected to
develop an algorithm for an error and exception case
free program.
 Intelligent visualization skills and prediction of end-
user actions on a particular event prevents errors
from occurring in the first place.
 The programmer is expected to test return values
from a function.

9. The Classic approach To Exception
Handling
 Each function returns a value indicating success or failure.
 Every function must check the return code of every function
call it makes and take care of errors.
 Exceptions make it easy to separate error handling from the
rest of the code.
 Exceptions make it easy to separate error handling from the
rest of the code.
 Intermediate functions can completely ignore errors
occurring in functions they call, if they can't handle them
anyway.

10. Methods of Exception Handling
 There are two methods to handle an exception in C.
 if - else method
 setjmp() and longjmp() method

11. 1. if - else method
 Exception is handled by making decisions via if – else.
 Occurrence of an exception is checked by the return
values of a function or by defined parameters.
 Along with that condition is placed an if – else
statement that checks and performs the respective
action against that exception.

12. 1. if - else method (cont..)
main()
{
code…
EXCEPTION
if (n == exception condition)
printf(“Operation cannot be performed”);
/*here we have to decide whether to exit the program or to ignore the
exception and run the program anyway */
else continue
code…
}

13. 2. setjmp () and longjmp() method
 setjmp() and longjmp() are used to jump away from a
particular location in a program into another
function.
 The programmer written code, inside that function
handles the exception
 To test the occurrence of an exception the setjmp()
function is called up.
 setjmp() saves the most recent event of the program
before that statement in a buffer called jmp_buf

14. 2. setjmp () and longjmp() method
(cont..)
 As soon as the exception test is complete the
setjmp() returns a value to the function.
 If the value returned from the setjmp() to the
longjmp() is ‘0’ it means that there was an exception
condition.
 Now the program will again start from the same
point where it stopped (saved in the buffer), until the
exception condition is removed or repaired.
 On the other hand programmer can also display
error messages or other fool-proof techniques.